The present invention relates to a fire barrier wall which includes an intumescent material, and, in particular, to a two hour fire barrier wall which includes a single layer of gypsum board secured to each side of the studs within the wall and an intumescent material barrier, such as but not limited to: an intumescent coating layer containing expandable particulate graphite applied to the interior or exterior of one or both gypsum board layers; a fibrous insulation blanket, located intermediate the gypsum board layers, with an intumescent material (e.g. an intumescent coating) layer on one or both surfaces of the blanket; a woven or non-woven fibrous mat layer or layers coated with an intumescent coating containing expandable particulate graphite located on the exterior of or intermediate the gypsum board layers; or a woven or non-woven fibrous mat layer or layers with expandable particulate graphite dispersed throughout the mat located on the exterior of or intermediate the gypsum board layers or combinations thereof.
Gypsum board fire barrier walls 120, having two hour performance ratings, are currently constructed, as shown in FIG. 6. As currently constructed, these two hour fire barrier walls 120 include two layers 122 and 124 of vertically extending five-eights of an inch, type X, gypsum wallboard attached by screws to both sides of metal screw or wooden studs 126 that are spaced apart on sixteen or twenty four inch centers. The cavity defined by the interior surfaces of the inner gypsum boards and the studs is filled with an insulation material 128, such as a glass fiber or mineral wool insulation blanket. While performing as required, the use of two layers of gypsum wallboard (each wallboard layer weighing approximately 2200 pounds/thousand square feet) on both sides of the studs in these fire barrier walls adds significantly to the weight to be supported by the structural framework of a building. In addition, the time and labor involved in handling and installing two layers of gypsum wallboard on each side of the studs can add to the construction costs. Thus, there has been a need for an inexpensive, easy to install, gypsum board fire barrier wall with a two hour performance rating that does not require the use of two layers of gypsum wallboard on both sides of the studs.
Intumescent materials, such as those disclosed in U.S. Pat. No. 3,574,644; issued Apr. 13, 1971; Franciszek Olstowski et al (hereinafter "the '644 patent), can be applied (as stated in column 3, lines 1-5 of the '644 patent) in the form of a coating to "normally combustible or heat degradable materials such as wood, fiber-board, plastics, insulative ceilings or wall panels, other cellulosic building materials, or the like" to increase the flame resistance of such normally combustible or heat degradable materials. These intumescent materials form passive fire protection systems which remain inactive until subjected to heat and temperatures such as those encountered from the flames of a fire. When these passive fire protection systems are subjected to heat and temperatures, such as those encountered in a fire, these intumescent materials react, grow and expand forming a char (many times the original thickness of the coating applied) to insulate the surface to which the material is applied from the damaging effects of the heat generated by the fire.
While these materials can be quite effective as fire barriers, these intumescent materials can be corrosive to steel, stainless steel, copper, aluminum and other metals or metal alloys, such as those commonly used in the construction industry. Thus, in applications, where these intumescent materials come in contact with metal components, e.g. metal fasteners such as screws or nails used to secure gypsum board to studs, the metal studs and other metal structural members or utilities such as piping and the like, the use of these intumescent materials can cause corrosion problems and although the disclosure of the '644 patent has been available to the construction industry for over twenty five years, gypsum board fire barrier walls are still constructed, as set forth above and shown in FIG. 6, using two layers of gypsum wallboard on both sides of the studs.